图书信息库完整解决方案（三）解析图书分类

经过综合对比分析（此处省略几千字），最终选定了HtmlUnit作为网页解析的工具。

通过maven来引入HtmlUnit资源包：

<groupId>net.sourceforge.htmlunit</groupId>
　　<artifactId>htmlunit</artifactId>
　　<version>2.28</version>
</dependency>

下面是解析图书分类的核心逻辑，大量的精力是要放在分析网页源码上，从中找出一级级的节点规律，然后再解析出自己需要的数据。

public List<BookCategory> categoryFromDangdang() {

        List<BookCategory> lsCategory = new LinkedList<BookCategory>();
        
        String categoryUrl = "http://category.dangdang.com/?ref=www-0-C";
        
        try {
            HtmlPage page = webClientGetPage(categoryUrl,false, false, null);
            
            List<DomElement> ll =  page.getElementsByTagName("div");
                        
            DomElement bookElement = null;
            for(int i=0;i<ll.size();i++) {
                DomElement e = ll.get(i);
                
                String s = e.getAttribute("class");

                if(s.equalsIgnoreCase("classify_con")) {
                    System.out.println("find book. class="+s);
                    
                    //在整个html中找到图书的一级节点
                    bookElement = e;
                    break;
                }
            }
            
            if(bookElement != null) {
                DomElement eClassify_books = bookElement.getFirstElementChild().getFirstElementChild();
                String s = eClassify_books.getAttribute("class");
                
                //找到图书分类的解析区域
                if(s.equalsIgnoreCase("classify_books")) {
                    System.out.println("find classify_books. class="+s);

                    String rootCategory = "";
                    
                    Iterable<DomElement> elementIterable = eClassify_books.getChildElements();
                    for (java.util.Iterator<DomElement> i = elementIterable.iterator(); i.hasNext(); ) {
                        DomElement e = (DomElement) i.next();
                        s = e.getAttribute("class");
                        
                        //图书分类的描述
                        if(s.equalsIgnoreCase("classify_books_detail")) {
                            DomElement eRoot = e.getElementsByTagName("h3").get(0).getFirstElementChild();
                            String url = eRoot.getAttribute("href");
                            String name = eRoot.getTextContent();
                            
                            rootCategory = urlToCategory(url);
                            System.out.println("find book rootCategory." + " name=" + name + " category=" + rootCategory);
                        }
                        //图书具体分类
                        else if(s.indexOf("classify_kind") != -1) {
                            DomElement eCategory = e.getFirstElementChild().getFirstElementChild();
                            String url = eCategory.getAttribute("href");
                            String name = eCategory.getTextContent();
                            
                            String category = urlToCategory(url);
                            if(category.equalsIgnoreCase("cp01.59.00.00.00.00"))//繁体字显示有问题
                                name = "港台图书";
                            System.out.println("find book category. " + " name=" + name + " category=" + category);    
                            
                            BookCategory bookCategory = new BookCategory();
                            bookCategory.setTitle(name);
                            bookCategory.setCategory(category);
                            bookCategory.setCategory_parent(rootCategory);
                            bookCategory.setCache(0);
                            
                            lsCategory.add(bookCategory);
                            
                            //二级分类
                            DomElement ul = e.getElementsByTagName("ul").get(0);
                            DomNodeList<HtmlElement> ulList = ul.getElementsByTagName("li");
                            
                            for(int j=0;j<ulList.size();j++) {
                                HtmlElement he = ulList.get(j);
                                if(he.getAttribute("name").equalsIgnoreCase("cat_3")) {
                                    DomElement eSubCategory = he.getFirstElementChild();
                                    
                                    url = eSubCategory.getAttribute("href");
                                    name = eSubCategory.getTextContent();
                                    
                                    String subCategory = urlToCategory(url);
                                    System.out.println("===========find book sub category. " + " name=" + name + " category=" + subCategory);    
                                    
                                    BookCategory bookSubCategory = new BookCategory();
                                    bookSubCategory.setTitle(name);
                                    bookSubCategory.setCategory(subCategory);
                                    bookSubCategory.setCategory_parent(category);
                                    bookSubCategory.setCache(1);
                                    
                                    
                                    lsCategory.add(bookSubCategory);
                                }
                            }
                        }
                    }
                }
            }
            
            //stringToFile(result,"E:\category.html");
        } catch (Exception e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            System.out.println("Exception="+e);
        }
        
        System.out.println("find book category finish. ");
        
        return lsCategory;
    }

解析出来的分类如下图所示：

这样就获取到了当当的所有图书分类，因为分类数据只有一个页面，所以相对比较简单一些。

另外还可以解析分类下的第一个页面，从而可以获取到关联分类下的网页页数和图书数量。